1. Field of the Invention
The present invention relates to a golf club head with high moments of inertia. More specifically, the present invention relates to a golf club head with a high moment of inertia achieved through the use of a deep aft cavity.
2. Description of the Related Art
Golf club companies have been increasing inertia properties of drivers to increase their performance particularly off center ball speed. The conventional shape of a driver limits the inertial values for a given head weight that can be attained within the dimension rules set by the USGA. Designs such as the FT-i® Driver from Callaway Golf Company have used non traditional shapes to increase inertia but the volume rule limits the potential efficiency of the location of discretionary weight placement. Designs that make use of light sections or light material to increase the amount of discretionary mass usually do not or can not (because of shape inefficiencies) place the discretionary mass in locations that provide the highest inertial benefit. Callaway Golf's FUSION® technology allows weight to be placed for high inertia by reducing the amount of weight tied up in the body of the club where inertia value is low.
The Rules of Golf, established and interpreted by the United States Golf Association (“USGA”) and The Royal and Ancient Golf Club of Saint Andrews, set forth certain requirements for a golf club head. The requirements for a golf club head are found in Rule 4 and Appendix II. A complete description of the Rules of Golf are available on the USGA web page at www.usga.org. One such limitation is the volume of the golf club head.
Existing driver heads are generally bulbous shaped bodies with a distinct striking face, crown and sole surfaces that are blended into a contiguous enclosed volume. These existing head shapes may be pear shaped, square, triangular or the like when viewed from above. Further, the shapes generally have a continuous perimeter outline consisting of face, heel, toe and aft edges. These heads can achieve reasonably high levels of inertia (Iyy and Izz) by placing discretionary weighting in the aft corners or aft center of these shapes. However, these shapes have a common deficiency in that they all have shell mass, area and volume in the center and back center regions (shaded area in views below) of the head that is relatively inefficient from an inertial standpoint.
Some drivers have been designed to address this issue by using aft concavities to reduce the amount of shell mass in this inefficient location. However, these drivers had other shortcomings. The Nassau driver, for instance, had a shallow face-aft dimension and little aft volume for aft weighting; it also had a low over-all head volume, both contributed to relatively low inertia. The hollow point driver was deeper and had more aft volume for weighting but was still relatively small volume. Further, it had an “extreme concavity” rendering the design visually unappealing and non-conforming to the USGA and R&A rules of golf.